Models Predict “Megadrought” Risk for American Southwest This Century

Near the beginning of the American Association of the Advancement of Science (AAAS) conference in San Jose, CA, on a winter day that happened to be warm, dry, and sunny, research scientists held a press conference to announce the conclusions of their work on predicting the risks of future “megadroughts.” They published their paper with the ominous title, “Unprecedented 21st-Century Drought Risk in the American Southwest and Central Plains,” in the first issue of Science Advances, a new digital, open-access journal. (The publisher, Marcia McNutt, gave brief opening remarks about how the journal will “showcase new and exciting research.”)

Benjamin Cook (NASA Goddard Institute), Toby Ault (Cornell University), and Jason Smerdon (Columbia University) obtained surprising results from computer model simulations. According to Cook and Smerdon, who videoconferenced with a shared microphone, previous models—such as those used for the IPCC’s 4th Assessment Report—underpredicted drought risks. Cook and his colleagues used drought records documented in more than 1800 tree-ring chronologies over the the past millennium, where ring width decreases in dry years, to develop 17 model projections of 21st century climate in the American Southwest and Central Plains. Their disturbing findings include predictions of megadroughts, lasting 35 years or longer, in both regions worse than any seen in the last 1000 years. In short, they expect climate change to increase drought length and severity in the coming decades.

Mean summer soil moisture and Palmer Drought Severity Index out to 2099. Courtesy: Cook et al. (2015)

Mean summer soil moisture and Palmer Drought Severity Index out to 2099. Courtesy: Cook et al. (2015)

The drought risk is twofold, due to reduced precipitation and to warmer temperatures drying out soils of rivers and lakes, in which models predict increasing evaporation. Long droughts due to climate variations have occurred in the past, such as those occurring during the 12th and 13th centuries (the Medieval Climatic Anomaly) that serve as important benchmarks. But with their tree-ring based reconstruction of the climate history, in a “business-as-usual” emissions scenario, they predict a “persistent shift in the future toward longer droughts” that could exceed even those of these extremely dry centuries.

Ault described how risk assessments are made, in terms of the magnitude of impact and the likelihood. “The levels [of risk] that we see are striking,” with an 80% or higher risk of a drought 35 years or longer in duration by the end of this century if climate change is not mitigated. He described the situation like a golf course, which an initial 10% of it consisting of sandpits. If climate change continues unmitigated, the golf course will gradually become almost entirely sandpits!

Risk (%) of decadal and multidecadal drought calculated from three sets of models. Courtesy: Cook et al. (2015)

Risk (%) of decadal and multidecadal drought calculated from three sets of models. Courtesy: Cook et al. (2015)

In the paper, Cook and his co-authors comment on the difficulties people in the Southwest and Central Plains will face when attempting to adapt to these climate conditions. In particular, the current depletion of nonrenewable groundwater reservoirs “will likely exacerbate the impacts of future droughts.” They discussed implications for both the water supply and food supply in the press conference, considering the dependence on agriculture in California and the breadbasket in the Central Plains. “Water security is food security,” as Ault put it, and people need to “take a no-regrets attitude toward preparedness.” Droughts will inevitably occur, and some of them could be as destructive as large earthquakes and hurricanes.

Their ongoing research will focus on examining the future severity, persistence and geographical scope of droughts, and they will attempt to improve the spatial resolution of their simulations, which currently employ coarse-grained averaging. They also plan to consider hydrology and snowpack, in addition to soil moisture. In any case, the soil moisture metrics and PDRI all point to one conclusion: unless people find a way to substantially mitigate climate change and prevent rising temperatures, the American Southwest and Central Plains can expect to face megadroughts like they’ve never seen before.

Finally, if you’re interested, below you can see my photo from the press conference (and I’m the one in the lower left with a cellphone in front of his face.) In other coverage of these results, see this nicely written Science article by Emily Underwood, and I saw a Washington Post reporter writing an article about it too (but I forgot his name), so watch for that.


All Aboard to the American Astronomical Society Meeting!

I’m on a train adventure, going through California, Oregon, and Washington to the American Astronomical Society (AAS) meeting in Seattle. This post is a modified version of one I wrote for the AAS
Sustainability Committee.

For those of you astronomers and journalists at the meeting, you’re welcome to join us for our Special Session next Wednesday (7th January) at 12:30-14:00 in Room 4C-3. We’ll be starting the new year with ideas and plans for addressing climate change issues in class and with the media.

We encourage anyone who is interested in the Sustainability Committee to contact us and get involved. We will post resources on this website for teaching and discussing climate change with journalists.

It’s important for astronomers to try to make observatories, telescopes, university department buildings, and computer centers as energy efficient as possible, but our largest environmental impact and carbon footprint comes from airplane flights to meetings, conferences, workshops, etc. According to a New York Times article, air travel emissions account for about five percent of global warming, and that fraction is projected to rise significantly as the volume of air travel is increasing much faster than gains in flight fuel efficiency.

It would help this situation to develop better resources and technologies for videoconferencing and remote observing, and these are areas where we should continue to make improvements. In addition, long-distance travel can be difficult for some people, such as for those with families and those in relatively remote locations, and videoconferencing and webcasts can make conferences more accessible to more people.

Nonetheless, long-distance travel is sometimes necessary, including for early-career scientists who need to advertise their work and network at conferences. I joined the Sustainability Committee in 2014, and one thing I am trying to do and trying to encourage others to do is to take more trains. In the US, long-distance trains can be very useful depending on where one wants to travel. They are not always the fastest mode of transportation, but they are comfortable, convenient, have great views, and usually have wireless access if you need to work. And importantly, they save energy.

I work at the University of California, San Diego, and I’m taking the train up the Pacific coast to Seattle via Los Angeles, Santa Barbara, which we just passed, the Bay Area, Sacramento, and Portland. (It makes me think of Woody Guthrie’s “This Land Is Your Land.”) I’m traveling nearly 1500 miles (2400 km)—nearly the entire distance from the southern to northern border of the US. As I wrote in a blog post last summer, Amtrak trains expend about 1,600 BTUs of energy per passenger per mile, while planes use 2,500 and cars use 3,900. Trains are much more energy efficient than planes, cars, and buses, and by not flying to Seattle, I’m saving tons of carbon dioxide emissions. This is just a start, but I am trying to view flying as a luxury or necessary evil that I will avoid and reduce when possible.

In any case, I’m excited to be part of the new and improved Sustainability Committee, and if you’re interested, join us at the AAS meeting! More importantly, make a resolution in 2015 to reduce your and your institution’s carbon footprint.

Innovating Regulatory and Business Models in the Electric Industry (because climate change)

At a Climate and Energy Law Symposium at the University of San Diego on Friday (7th November), scientists, policy experts, lawyers, and business leaders gathered to discuss trends driving changes in the electric industry and regulatory and business responses to them. It was a rather sunny and hot day for southern California in November, perhaps highlighting ongoing climate change and the need to adapt the regulatory framework, market rules, and interactions between electric utilities and customers. The symposium was titled, “Innovative Regulatory and Business Models in a Changing Electric Industry.”

The symposium seemed to lean more on the business and legal side of things rather than the policy and science side, so I was out of my element, but I’ll try to write about some of the interesting things I learned there. USD also publishes the San Diego Journal of Climate & Energy Law, if you’d like to read more about related topics.


In one of the morning sessions, Jamie van Nostrand from West Virginia University spoke about drivers of electric industry innovations including climate change mitigation and adaptation—for example following the experience of Superstorm Sandy. The electric industry is adapting to the rapid expansion of photovoltaics and solar panels in recent years and is preparing for the growth of “distributed energy” stored in small, decentralized grid-connected devices. (These images of rooftop solar and smart-grid technology are courtesy of NREL and DOE.)


These were common themes throughout the day, especially the growth of solar and the proliferation of distributed energy resources. Although Sky Stanfield (at Keyes, Fox, & Wiedman LLP) stated that the increasing number of grid-connected solar installations has been mostly in the residential sector, as you can see from this recent report by the Union of Concerned Scientists, solar PV is growing exponentially in residential as well as commercial and large-scale sectors in the US.


Of course, some countries, such as Germany, have surpassed these levels. Germany now generates as much as ~30% of its electricity from renewables, mostly from solar and wind power. The government’s goal is to double that amount by 2035, and they’re on track to successfully do so. However, in the meantime, they need to address issues of adapting the electrical grid and constructing new grid-storage capacity—issues also faced by the US electric industry.

Distributed energy, such as with rooftop solar panels, has the potential to allow individuals and communities to have more power (no pun intended) and influence with respect to utilities. Distributed generation could not just decentralize but also even democratize electricity systems, although that seems a little overoptimistic to me (see this article in Grist). Some states have witnessed opposition to distributed generation and to “net metering,” in which an electricity consumer who generates on-site electric energy (such as with solar panels) can offset part of their electricity bill. Some people have portrayed that as “free riding,” and Troy Rule (Arizona State Law School) showed this anti-net metering advert, which is ridiculous and funny as propaganda.

So what’s next? Kevin Jones (Vermont Law School) talked about five environmental pathways for an improved electric grid in his book, “A Smarter, Greener Grid,” including things like distributed energy technologies and optimization, electric vehicles, and areas to improve energy efficiency. Dian Grueneich, a former Public Utilities Commissioner, outlined proposals for “California’s Electricity Policy Future: Beyond 2020.” This included updated net-metering policies so that individuals and communities could more easily share a solar project’s electricity output. More importantly, she argued for a inter-agency policymaking structure that integrates electricity with climate, water, air quality, and transportation goals.

For all their talk of “innovation” (or even “disruptive innovation”!), I can’t say I left feeling like these people are transforming the electric industry in a fundamental way; they’re just gradually adapting to worsening climate change, which means more people with solar panels and making grids less vulnerable to Sandy-like storms. They’ll have to adapt to much more than that, judging from the conclusions of the newest IPCC report.

But what do Californians, industries, and policy-makers really need to do to mitigate, and not just adapt to, climate change? The symposium, which included speakers from and was sponsored by San Diego Gas & Electric, made inroads but only touched the surface of this question. The final person to ask a question during the final Q&A period referred to this issue, but her question remained unanswered and was postponed to the reception, where alcohol would be served.

Californians and the Environment

The Public Policy Institute of California (PPIC), a nonprofit, nonpartisan thinktank based in San Francisco, recently conducted a survey of Californians’ views of environmental issues. This is particularly important in light of the ongoing drought in the southwest and the upcoming elections in November. According to the report (available in PDF format), the results are based on the responses of 1,705 adult residents throughout California, interviewed in English and Spanish by landline or cell phone, and they’re estimated to have a sampling error of 4% (at the 95% confidence level). I’ll describe what I see as their most interesting results, and if you want more information, I encourage you to read the report.

Global warming: A strong majority say they are very concerned (40%) or somewhat concerned (34%) about global warming. Approximately two thirds of Californians (68%) support the state law, AB 32, which requires California to reduce its carbon emissions to 1990 levels by 2020, but the partisan divide (Democrats at 81% vs Republicans at 39%) has grown on this issue. 80% of Californians say that global warming is a very serious or somewhat serious threat to the economy and quality of life for California’s future. Only 45% of people are aware at all about the state’s cap-and-trade system, which took effect in 2012, but after being read a brief description, Californians are more likely to favor (51%) than oppose (40%) the program. Under a recent agreement between the governor and legislature, 25% of the revenues generated by the cap-and-trade program will be spent on high-speed rail, 35% on other mass transit projects and affordable housing near transit, and the rest for other purposes.


Energy policies: overwhelming majorities of adults favor requiring automakers to significantly improve the fuel efficiency of cars sold in the U.S. (85%) and increasing federal funding to develop wind, solar, and hydrogen technology (78%). Strong majorities support the requirement that oil companies produce cleaner transportation fuels and the goal that a third of California’s electricity come from renewable energy sources. But residents’ support declines significantly if these two efforts lead to higher gas prices or electricity bills. (This is unfortunate, because gas and oil companies are heavily subsidized in the US, and maybe our gas and electricity bills are too low.) Most residents (64%) oppose building more nuclear power plants, as they have since the Fukushima disaster.

The survey includes other contentious issues: 54% of Californians oppose hydraulic fracturing, or fracking, for oil and natural gas extraction. But a majority (53%) support building the Keystone XL pipeline.

Water policies: Asked about some of the possible effects of global warming in California, majorities say they are very concerned about droughts (64%) or wildfires (61%) that are more severe. 35% say that water supply or drought is the most important environmental issue facing the state today (which is 27% higher than the fraction in a 2011 survey), and this is the first environmental survey in which air pollution was not the top issue. In another measure of concern about drought, strong majorities of residents (75%) say they favor their local water districts requiring residents to reduce water use. The CA legislature is discussing a $11.1 billion state bond for water projects that is currently on the November ballot, and a slim majority of likely voters would support it (51% yes, 26% no).

If you’re interested, the PPIC has useful information and publications on water policies and management of resources: see this page and this blog post series. Water policy analysts argue that in the Central Valley, where most agricultural water use occurs, the failure to manage groundwater sustainably limits its availability as a drought reserve. In urban areas, the greatest potential for further water savings lies in reducing landscaping irrigation—a shift requiring behavioral changes, not just the adoption of new technology. Finally, state and federal regulators must make tough decisions about how and when to allocate water during a drought: they must balance short-term economic impacts on urban and agricultural water users against long-term harm—even risk of extinction—of fish and wildlife.

People’s Climate March

This is a different topic and has nothing to do with the survey, but I want to use this opportunity to plug the People’s Climate March, which will be taking place on Sunday. (This website can direct you to events in your area.) One of the biggest marches and rallies will be in New York City, where the UN climate summit will soon be taking place. Even Ban Ki-moon will be participating! For San Diegans, you can find information about Sunday’s downtown events here. Californians also organized a “People’s Climate Train” to take activists and participants by train from the Bay Area through Denver and Chicago to New York, where they’ll be arriving tonight. Finally, I recommend reading this well written piece by Rebecca Solnit on Dr. Seuss’s The Lorax and the need to raise our voices on Sunday.

For Traveling Scientists: Praise for Trains

And now for something completely different! I’d like to make the case that we should take intra-city and inter-city trains more often. (I mean this especially for Americans, since trains are already more popular and more advanced in many other countries.) As some of you know, I like riding trains, and I even thought of writing an “ode to trains,” but though I enjoy poetry—which is virtually required of me as a half-Persian—I don’t think I write it particularly well. One of my first memories as a boy was riding a train in Colorado and sticking my head out the window, only to get a face full of smoke. I’m a fan of blues, folk, and jazz music too, and many musicians (such as Woody Guthrie, Muddy Waters, Johnny Cash, Bob Dylan, Joan Baez) have sung train songs. This post is also partly inspired by an interesting and entertaining article by Kevin Baker in the July 2014 issue of Harper’s magazine.

I’m motivated by the fact that many people, and especially scientists, frequently travel long distances. Many astronomers and astrophysicists travel to conferences, workshops, and meetings as well as to telescopes. Occasionally it’s possible to interact or participate in meetings by videoconferencing and to use telescopes with “remote observing,” but it’s often the case that travel can’t be avoided, and as I’ve written here before, it’s important for junior scientists to present their work and engage in networking in person to help to advance their careers. Although most telescopes and observatories are constructed to be environmentally friendly, it is long-distance travel that results in very large “carbon footprints.”

My carbon footprint has been particularly large this year, and I hope to do better next year. I plan to begin by considering taking a train from southern California to Seattle for the annual meeting of the American Astronomical Society (AAS) in early January. Long-distance travel is also an issue being taken up by the AAS Sustainability Committee.


If you’re wondering, this trip would take most of a weekend, but it would offer nice views of the Pacific coast and the trains have free wireless internet too. It looks like the Coast Starlight line takes about 34 hours to travel from Los Angeles’s historic Union Station (pictured below) to Seattle’s King Street Station, but it covers a distance of 1377 miles (2216 km)—nearly the distance between the borders of Mexico and Canada.


We should keep in mind that, after walking and biking, trains are the most efficient way to travel. Amtrak, the US’s publicly funded railroad service, expends an estimated 1,600 BTUs of energy per passenger per mile, while buses use 3,300, planes use 2,500, and cars use 3,900! If we seriously want to use less energy and substantially reduce carbon emissions, we should travel by train much more often. From the perspective of climate change, although “carbon offset” programs have been attempted (with very limited success so far), nothing beats not emitting greenhouse gases in the first place.

Americans used to travel all the time by train, but with the triumph of the auto and aviation industries and the increased popularity of cars (with subsidized gas prices) and planes for long-distance travel, Amtrak ridership dropped to 16 million in 1972. Fortunately, ridership has doubled since then, and President Obama in 2011 committed his administration to a vision of giving “eighty percent of Americans access to high-speed rail within twenty-five years.”

The US needs to upgrade and expand its train lines and cars. Europe and China have trains that are at least twice as fast as ours, and Japan’s new Shinkansen bullet train goes 200 mph! Americans sometimes complain that the country is too big for trains, but China shows that it’s certainly possible. I think we need to push for high-speed trains, especially in California and the East Coast but also within the country, such as the California Zephyr line that links the Bay Area, Denver, and Chicago. This will take a lot of investment and time, but it will be worth it. Although the US auto industry has suffered in recent years, improving and expanding the rail system certainly would help the “green economy” and create many “green jobs”. And we should keep in mind that annual federal highway and aviation subsidies are currently gigantic ($41.5 and $16 billion in 2013, respectively) compared to Amtrak subsidies ($1.6 billion). The planned California high-speed rail will cost an estimated $68 billion to construct, but it will be built over many years.

Will Climate Change Embolden the Environmental Justice Movement?

[I’m cross-posting this, which was originally posted on the Union of Concerned Scientists blog. Thanks to Melissa Varga for editing assistance.]

We are at an historic anniversary: the Civil Rights Act was enacted fifty years ago on the 2nd of July, 1964. According to the legislation, all persons “shall be entitled to the full and equal enjoyment of…any place of public accommodation, as defined in this section, without discrimination” based on race, color, religion, or national origin. It ended unequal application of voter registration requirements and racial segregation in schools, at the workplace and by facilities that served the general public. (Another milestone, Brown v. Board of Education, occurred sixty years ago.) The Civil Rights Act was initially about the important symbolism of inclusion. But what does this have to do with climate change?


We still need to address what sociologists refer to as institutionalized inequality and injustice. Randall Kennedy in Harper’s magazine asks, why has the struggle against racism been more effective in public accommodations than in schooling, housing, employment, and the administration of criminal justice? “What is the value,” the civil rights activist Bayard Rustin once asked, “of winning access to public accommodations for those who lack money to use them?” To address structural injustices and inequities, more action is required.

“Environmental justice” is meant to address a critical area where such injustices remain. Attorney General Eric Holder said in a speech at the Environmental Protection Agency in 2011 that Dr. Martin Luther King Jr. “plant[ed] the seeds of the environmental justice movement” and that environmental justice is “a civil rights issue.” The EPA defines environmental justice (EJ) as the “fair treatment and meaningful involvement of all people regardless of race, color, national origin, or income with respect to the development, implementation, and enforcement of environmental laws, regulations, and policies.” EJ often refers to water and air pollution, soil contamination, toxic hazards, power plants, industrial facilities, and environmental degradation that preferentially affect residential areas and communities with people of a particular race, ethnicity, or economic status. It also refers to social movements that have, with some success, attempted to rectify this.

EJ is also particularly relevant to climate change. Issues of “equity, justice, and fairness” were referred to in the latest IPCC report, and as argued by Union of Concerned Scientists Senior Climate Economist Rachel Cleetus in an earlier post, EJ should be considered as a major factor in President Obama’s Climate Action Plan. We are already seeing extreme climate events, including heat waves, floods, wildfires, and droughts, and poor coastal communities are particularly vulnerable to storm surges, coastal flooding, and rising sea levels. Although dangerous weather events appear to occur randomly, some people are more vulnerable than others and some receive more effective aid during cleanup and recovery. (See the book “Race, Place, and Environmental Justice after Hurricane Katrina”, edited by Robert Bullard and Beverly Wright.) Sometimes environmental laws are insufficient and federal agencies don’t take sufficient steps to protect workers and residents, and certainly there is room for improvement.

A few weeks ago, I attended a meeting on Climate Change Resilience and Governance in Washington, DC, which was organized by the American Association for the Advancement of Science (AAAS). The speakers included Jalonne White-Newsome, a former UCS Kendall Science Fellow now a policy analyst for WE ACT for Environmental Justice. She talked about how currently EJ communities are not engaged in the process, and the failure to mobilize the majority of Americans who want action on climate change is partly due to the fact that not everyone is part of the conversation. Many black, Latino, and Native American communities, as well as working class white communities, live closer to various polluting industries, landfills, fracking infrastructure, etc. than others, but they don’t have enough information about what they can do about it, how they can communicate with the authorities, or how to receive the aid they need. (For more on this meeting, see my blog post on it).

Scientists, activists, and policy analysts are now thinking about and addressing the causes and effects of climate change. Although we want to substantially reduce carbon dioxide emissions and avoid the worst of global warming, climate change is already happening. Throughout different regions of the US, we can expect more frequent and extreme droughts, floods, and heatwaves in the future (see the overview of the National Climate Assessment.

This is where climate adaptation and resilience come in, and this is what people are actively working on these days. For example, people on the top floors of poorly cooled buildings in dense urban areas are among the most vulnerable to heat waves, and simple solutions like white-painted roofs (see below) can save many lives. Scientists and medical experts are also studying the cumulative impact to the health of vulnerable populations, for example following natural disasters (such as hurricanes or floods) that also damage the social and physical infrastructure necessary for resilience and emergency response. Afterward, federal agencies need to be ready to help local organizations and communities with reconstruction. To address future water shortages and drought impacts, Congress authorized the National Integrated Drought Information System in 2006, which identifies drought-sensitive regions and manages drought-related risks and which involves the coordination of federal, state, local, regional, and tribal partners.


There is certainly plenty more work to do on climate mitigation and adaptation, and environmental justice should be a key element of it. As we look back on all we’ve accomplished since the Civil Rights Act was passed fifty years ago, let’s keep working to eliminate injustice and inequality as we prepare for the great challenge of the 21st century—climate change.

Climate Change is an Environmental Justice issue

In a previous blog post, I introduced the concept of environmental justice (EJ), which refers to the fair treatment of people regardless of race or class with respect to the development, implementation, and enforcement of environmental laws, regulations, and policies. I’ve also previously written about climate change here and about some efforts to address it here. Now my point here that climate change is an EJ issue, especially because anthropogenic greenhouse gas emissions (GHGs) have been primarily produced by people in wealthier countries, while people in poorer countries and regions will likely bear the brunt of the effects of climate change, including rising sea levels, drought, and access to food staples.

The new report from the Intergovernmental Panel on Climate Change (IPCC) was just released a week ago, soon before Earth Day. (You can read news coverage of the report in the Guardian, NY Times, and Atlantic.) The IPCC report was produced by 1,250 international experts and approved by 194 governments, and it is the last of three reports to assess climate research conducted since 2007. The authors argue that only an intensive push in the immediate future can limit climate change to less than catastrophic levels, but lowering costs of alternative energies have made transitioning on a mass scale practical and affordable. Avoiding (the worst of) climate change will be less costly than attempting to adapt to it later with unpredictable geoengineering technologies. The report also discusses “co-benefits“: for example, efforts to reducing air pollution (including GHGs) would improve public health and save millions of lives, balancing the cost of reducing the emissions. The report states that putting a price on GHG emissions, such as through carbon taxes or emission permits (which I’ll write about in a later post), would help to redirect investment toward more climate-friendly technologies and away from fossil fuels.

It’s also interesting to see what was not included in the IPCC report. For example, rich countries (including the US) pushed to remove a proposed section that called for hundreds of billions of dollars of aid per year to be paid to developing countries. The report does refer to “issues of equity, justice, and fairness [that] arise with respect to mitigation and adaptation,” but these are issues that should be further discussed and addressed. For example, we are already seeing extreme climate events, including heat waves, floods, wildfires, and droughts, and poor countries and small island nations are particularly vulnerable to storm surges, coastal flooding, and rising sea levels.

In order to mitigate climate change, the report views favorably the cutting energy waste and improving efficiency and the shift toward renewable energies, especially the zero-emission sources like wind and solar, whose costs are dropping and becoming competitive. Wealthier countries can lead these efforts, and they could fund low-carbon growth in poorer countries, which are unfortunately expanding the use of coal-fired power plants. Archbishop Desmond Tutu has even advocated for an anti-apartheid style campaign against ­fossil fuel companies to respond to the “injustice of climate change.” On that note, I’ve noticed that the term “climate justice” has become increasingly common.

Many vulnerabilities to climate change are visible in the US as well (see this UCS blog), and much more can be done to work toward climate change mitigation and adaptation. In addition, unfortunately, climate change has not yet been connected to EJ in US policy, in spite of the Executive Order signed by Pres. Bill Clinton twenty years ago, which instructed all federal agencies to consider impacts on people of color, the elderly, and those of low-income when crafting new policies and rules. (See this post by post by Robert Bullard, one of the leaders of the EJ movement.) The Environmental Protection Agency’s new Plan EJ 2014 briefly mentions climate change, and at least this is a start.

In order to mobilize people, governments, and institutions to active address climate change, we should discuss how climate change issues are framed. A week ago, I attended an interesting political science talk by Sarah Anderson, professor of environmental politics at UC Santa Barbara. (By the way, I have to admit that the political scientists at UCSD have more comfy chairs than us astrophysicists. We’ll have to work on that!) She mentioned the “moral foundations theory” (proposed by Jonathan Haidt; and Lakoff & Wehling): political liberals construct their moral systems primarily upon two psychological foundations (fairness/justice and harm/care), while conservatives’ moral systems are also based on others (including ingroup/loyalty, authority/respect, purity/degradation). So if the goal is to address climate change–which may be one of the greatest environmental and socioeconomic problems of our generation–then we should try to appeal to everyone, not just those identified as liberals or leftists. To do so, maybe we need to use additional frames, such as by emphasizing the importance of avoiding environmental degradation and the potential economic benefits of mitigating climate change.

Finally, political scientists often focus on the workings of the state and on policies and regulations, but there are many important actors outside the state, especially among social movements and civil society. Fortunately, organized opposition to the Keystone pipelines and fracking, for example, have made these climate change issues more pressing for policy-makers.
Harvard poli sci professor Theda Skocpol (quoted in a New Yorker article) criticizes the tactic of mobilizing support exclusively through the media; instead, she argues, “reformers will have to build organizational networks across the country, and they will need to orchestrate sustained political efforts that stretch far beyond friendly Congressional offices, comfy board rooms, and posh retreats.” Perhaps what the environmental movement need are more “federated structures,” which have national leaders to interact with political officials in the White House and Congress as well as local chapters which regularly meet (and organize rallies or teach-ins) to develop their larger goals.

How scientists reach a consensus

Following my previous post on paradigm shifts and on how “normal science” occurs, I’d like to continue that with a discussion of scientific consensus. To put this in context, I’m partly motivated by the recent controversy about
Roger Pielke Jr., a professor of environmental studies at the University of Colorado Boulder, who is also currently a science writer for Nate Silver’s FiveThirtyEight website. (The controversy has been covered on Slate, Salon, and Huffington Post.) Silver’s work has been lauded for its data-driven analysis, but Pielke has been accused of misrepresenting data, selectively choosing data, and presenting misleading conclusions about climate change, for example about its effect on disaster occurrences and on the western drought.

This is also troubling in light of a recent article I read by Aklin & Urpelainen (2014), titled “Perceptions of scientific dissent undermine public support for environmental policy.” Based on an analysis of a survey of 1000 broadly selected Americans of age 18-65, they argue that “even small skeptical minorities can have large effects on the American public’s beliefs and preferences regarding environmental regulation.” (Incidentally, a book by Pielke is among their references.) If this is right, then we are left with the question about how to achieve consensus and inform public policy related to important environmental problems. As the authors note, it is not difficult for groups opposed to environmental regulation to confuse the public about the state of the scientific debate. Since it is difficult to win the debate in the media, a more promising strategy would be to increase awareness about the inherent uncertainties in scientific research so that the public does not expect unrealistically high degrees of consensus. (And that’s obviously what I’m trying to do here.)

Already a decade ago, the historian of science Naomi Oreskes (formerly a professor at UC San Diego) in a Science article analyzed nearly 1000 article abstracts about climate change over the previous decade and found that none disagreed explicitly with the notion of anthropogenic global warming–in other words, a consensus appears to have been reached. Not surprisingly, Pielke criticized this article a few months later. In her rebuttal, Oreskes made the point that, “Proxy debates about scientific uncertainty are a distraction from the real issue, which is how best to respond to the range of likely outcomes of global warming and how to maximize our ability to learn about the world we live in so as to be able to respond efficaciously. Denying science advances neither of those goals.”

The short answer to the question, “How do scientists reach a consensus?” is “They don’t.” Once a scientific field has moved beyond a period of transition, the overwhelming majority of scientists adopt at least the central tenets of a paradigm. But even then, there likely will be a few holdouts. The holdouts rarely turn out to be right, but their presence is useful because a healthy and democratic debate about the facts and their interpretation clarifies which aspects of the dominant paradigm are in need of further investigation. The stakes are higher, however, when scientific debate involves contentious issues related to public policy. In those situations, once a scientific consensus appears to be reached and once scientists are sufficiently certain about a particular issue, we want to be able to respond effectively in the short or long term with local, national, or international policies or regulations or moratoria, depending on what is called for. In the meantime, the debates can continue and the policies can be updated and improved.

Of course, it is not always straightforward to determine when a scientific consensus has been reached or when the scientific community is sufficiently certain about an issue. A relevant article here is that of Shwed & Bearman (2010), which was titled “The Temporal Structure of Scientific Consensus Formation.” They refer to “black boxing,” in which scientific consensus allows scientists to state something like “smoking causes cancer” without having to defend it, because it has become accepted by the consensus based on a body of research. Based on an analysis of citation networks, they show that areas considered by expert studies to have little rivalry have “flat” levels of modularity, while more controversial ones show much more modularity. “If consensus was obtained with fragile evidence, it will likely dissolve with growing interest, which is what happened at the onset of gravitational waves research.” But consensus about climate change was reached in the 1990s. Climate change skeptics (a label which may or may not apply to Pielke) and deniers can cultivate doubt in the short run, but they’ll likely find themselves ignored in the long run.

Finally, I want to make a more general point. I often talk about how science is messy and nonlinear, and that scientists are human beings with their own interests and who sometimes make mistakes. As stated by Steven Shapin (also formerly a professor at UC San Diego) in The Scientific Revolution, any account “that seeks to portray science as the contingent, diverse, and at times deeply problematic product of interested, morally concerned, historically situated people is likely to be read as criticism of science…Something is being criticized here: it is not science but some pervasive stories we tend to be told about science” (italics in original). Sometimes scientific debates aren’t 100% about logic and data and it’s never really possible to be 0% biased. But the scientific method is the most reliable and respected system we’ve got. (A few random people might disagree with that, but I think they’re wrong.)

Water Policy Issues, with a Focus on the US Southwest

Water policy issues are very important, but we haven’t discussed them much on this blog yet. Much of my information here comes from Ellen Hanak and other analysts of the Public Policy Institute of California (PPIC), analysts from the Union of Concerned Scientists (UCS), a recent article by Christopher Ketchum in Harper’s, a book by Robert Glennon (Unquenchable), and other sources. I’m not an expert on water policy, and any errors are my own. As usual, please let me know if you notice any errors, and I’m happy to hear any comments. I’ll focus on the southwestern US (mainly because I grew up in Colorado and now live in California), but many of these issues apply elsewhere as well. And while the Southwest is dealing with drought and water scarcity, other places, such as the UK and the Midwest US, are dealing with flooding.


According to the Worldwatch Institute, already some 1.2 billion people live in areas of physical water scarcity, while another 1.6 billion face “economic water shortage”. By 2025, almost half of the world will be living in conditions of water stress. Some analysts predict that water wars (see Vandana Shiva’s book) and conflicts will increase in the future. Considering that we need water to live, it’s not surprising that the United Nations General Assembly voted in a resolution declaring that access to clean water and sanitation is a fundamental human right.

At least conditions on Earth are not as bad as Mars, which has experienced 600 million years of drought and which probably hasn’t supported life, at least on its surface. But water scarcity is an extremely important problem that we’re probably not taking seriously enough; as Stephen Colbert put it, “if the human body is 60 percent water, why am I only two percent interested?”

The Southwest and California in particular are experiencing their worst recorded drought (for example, see the NASA satellite images below). In response, the California state legislature and Gov. Brown passed a drought relief package last month, while Sen. Feinstein and others are seeking to pass a bill in Congress to aid drought-stricken states.


Now here’s some historical and legal context. The Colorado River Compact of 1922 was negotiated by members of the upper-basin states (Colorado, New Mexico, Utah, Wyoming) and the lower-basin states (Arizona, California, Nevada), and it was an agreement for hydraulic management of the Southwest. According to the US system of water rights, however, the person who first made “beneficial use” of a stream or river had first right to it. Under this doctrine, the earliest users of the Colorado River (California) could legally establish a monopoly over regional water supply, even though most of that water came from another state (Colorado). A major problem was that because 1922 happened to occur during an unusually wet period, people assumed that the Colorado held more water than it really did: its annual water flow as estimated to be 17-18 million acre feet, though it was later more accurately estimated at 14 million acre-feet (17 billion cubic-meters) on average. It was therefore already overallocated from the start. The lower basin (including southern CA) is now overusing its share of the Colorado River, and it’s not a sustainable situation. A court case (Arizona v. California) that was decided by the Supreme Court in 1963 affirmed that Arizona was owed 2.8 million acre feet of water annually, but under the doctrine of prior appropriation, Arizona’s rights would remain secondary to California’s.

For water use, it’s useful to distinguish between water withdrawal (from surface or ground sources) and the consumption of water already withdrawn. Consequently, as argued by Ellen Hanak at a recent PPIC event in Sacramento, we need to consider not just water supplies but also water management and (in)efficient water consumption. Although one usually thinks of water for drinking, washing, cleaning, and other residential uses, much more water is used for irrigation (agriculture), industry, and power plants; according to the UCS, power plants account for 41% of freshwater withdrawals in the US. It’s also useful to distinguish between direct and indirect water use, and I’ll get into that more below.

Water shortages, already a critical issue in the Southwest, are likely to become far worse with climate change (although the extent to which it’s due to climate change is still debated). Rivers such as the Colorado, which is primarily supplied by snowmelt and is already overallocated, are particularly vulnerable. For the past fourteen years, the Colorado River has been at its lowest level since the ninth century. According to Tim Barnett from UC San Diego’s Scripps Institution of Oceanography (SIO), with climate change, currently scheduled water deliveries from the Colorado River are unlikely to be met by mid-century. Rising air temperatures due to global warming will result in reduced snowfall: by the end of this century, California’s ski season could disappear with a 80% loss of Sierra snowpack, and Washington and Oregon would experience reduced snowfall as well. In addition, although per capita water use has been gradually decreasing, population growth in the Southwest is likely to increase urban water demand in some regions. In a high carbon emissions scenario, annual losses to agriculture, forestry, and fisheries could reach $4.3B in California alone, and the prices of fresh fruit, vegetables, dairy, and fish, will rise. There will be more competition between human water use and water needed to support fish and other wildlife, and potential solutions will involve difficult trade-offs. (The following figure from the EPA summarizes climate impacts on the hydrologic cycle.)


In the studies mentioned above by SIO scientists, the Colorado River’s average annual flow could decline by as much as 30% by 2050. As a result, without massively reducing water usage, Lake Mead has a 50% chance of declining to “dead pool” by 2036. At that level, water deliveries to millions of people in California and Arizona and to millions of acres of farmland will cease, and hydroelectric production at the dam will already have stopped. It is incredible to consider that this could happen in our lifetime, as the Colorado is the same river that carved the Grand Canyon over tens of millions of years, and it is one of the rivers on which the Ancient Puebloan depended until around 1300, when drought, decreased rainfall, and a drop in water table levels appeared to drive the people away from their civilization. (See also this article in National Geographic about ancient “megadroughts” in human history.)

The largest fraction of water consumption is due to agriculture, power plants, and industry. Considering the fact that we indirectly need water because of our need for energy, this points to the issue of the “water-energy nexus.” The average U.S. family of four directly uses 400 gallons of freshwater per day, while indirectly using 600-1800 gallons through power plant water withdrawals. We need energy for water production and distribution (and the desalination plant being constructed near San Diego will require quite a bit), and we also need water for energy-related infrastructure. Coal and nuclear power plants use large amounts of freshwater to cool the plants: for example, a typical 600-MW coal-fired plant consumes more than 2 billion gallons of water per year from nearby lakes, rivers, aquifers, or oceans. In addition, as we discussed in my previous blog post, fracking techniques for extracting shale gas require millions of gallons of water to be injected into a well, and they can contaminate groundwater as well. Fortunately, wind turbines and solar photovoltaic modules require essentially no water at all, but other renewable energies, like hydroelectric, bioenergy, and geothermal, can be water intensive. As argued by Laura Wisland, since we expect climate change to increase the frequency and severity of droughts in California, it will be important to hedge our electricity supplies with predictable, renewable resources, especially wind and solar.

What can be done? As a “silver lining” of the current situation, the ongoing drought in the Southwest provides a window for reform, and here are a few ideas. We should shift toward less water-intensive sources of energy such as wind and solar. Water should cost more: we should modernize water measurement and pricing with better estimates of water use and prices that reflect water’s economic value. We could learn from cities in dry places elsewhere (such as Australia) about how to make urban areas more water efficient, and we could have tiered water rates with higher prices for greater use. In agriculture, crops that cannot be grown without subsidies should not be grown. We need improvements to local groundwater management. Since surveys show that most Californians believe that there are environmental inequities between more and less affluent communities in the state, it’s also important to consider environmental justice issues while developing new water policy programs (see this article, for example). We need to develop more reliable funding (through state bonds or local ratepayers), especially for environmental management, flood protection, and statewide data collection and analysis. Finally, as argued in this PPIC report, water management agencies at all levels should aim to develop more coordinated, integrated approaches to management and regulatory oversight, drawing on scientific and technical analysis to support sound and balanced decisions.

The Physics of Sustainable Energy

I attended a conference this weekend called “The Physics of Sustainable Energy” at the University of California, Berkeley. It was organized by people affiliated with the American Physical Society, Energy Resources Group, and a couple other organizations. Most of the speakers and attendees (including me) seemed to be Californians. I had some interesting conversations with people and attended some great talks by experts in their fields, and here I’ll just give you a few highlights.

First though, I want to make two general comments. I did notice that only ~20% of the speakers were women, which is worse than astrophysics conferences, and it’s too bad the organizers weren’t able to make the conference more diverse. (There were a few people of color speaking though.) Secondly, I think it’s excellent that people (and not just in California) are actively involved working on solutions and innovations, but I think we should be careful about an technophilic or technocratic emphasis. This was a conference for physicists and engineers though, and energy policy and communication with the media and policy-makers, for example, were mostly beyond the scope of it. I was struck by the apparently close ties with industry some speakers had (such as Amory Lovins and Jonathan Koomey); to some extent that’s necessary, but I was a little concerned about potential conflicts of interest.

…On to the conference. Ken Caldeira spoke about the global carbon balance. When accounting for CO2 emission per capita from fossil fuel use and cement production: the US is worst (50kg CO2/person/day), followed by Russia, China and the EU. California emits half as much as the rest of this country, but 2/3 of the difference is due to a fortunate climate (it doesn’t get very cold); according to an audience member (Art Rosenfeld?), “we’re mostly blessed with good luck as well as some brains.” Daniel Kammen (one of the organizers) then talked about developing a framework for energy access for all. According to the International Panel on Climate Change (IPCC AR4 in 2007): “warming will most strongly and quickly impact the global poor.” Kammen described the concept of “energy poverty”: 1.4 billion people lack access to electricity today, and that will still be the case for a similar number in 2030, with more having unreliable/intermittent access. There appears to be a strong correlation between electricity access and human development index.


It seems that many people are working on interesting research & development on renewable energy sources. Jennifer Dionne spoke about the “upconversion” of solar cells, which includes thermodynamic, electronic, and photonic design considerations. The upconversion process improves cell efficiency by at least 1.5× (see Atre & Dionne 2011), and it often works well at optical near-infrared wavelengths. (She pointed out that of energy from the sun, 5% is in the UV, 43% in optical, and 52% in infrared. And if you’re interested in what those proportions are like for different types of galaxies, check out my recent paper.) Then Chris Somerville spoke about the status and prospects of biofuels, the production of which is currently dominated by the US and Brazil. The combustion of biomass has challenges for providing low-carbon energy: depends on tilling of soil, land conversion, fertilizer, transportation, and processing. I’m concerned about deforestation and effects on ecosystems as well as the effects on food/crop prices (remember the food riots in 2007-2008 and the rising cost of corn/maize?). In my opinion, Somerville didn’t sufficiently address this, though he did argue in favor of miscanthus and other biomass rather than the use of corn. John Dabiri spoke about the advantages of vertical-axis wind turbines (called VAWTs, see the figure above), in addition to the ubiquitous horizontal-axis variety. VAWTs have a smaller structure size and cost, simpler installation logistics, and are safer for birds and bats as well. Currently only four countries get >10% of their electricity from wind (Spain, Portugal, Ireland, Denmark, followed by Germany with 9%), but this can be easily improved.


This flow diagram is pretty nice, and it describes current energy use in the US (presented by Valerie Thomas). And Daniel Kammen, in a paper on the relation between energy use, population density, and suburbanization, shows the spatial distribution of carbon footprints (where the units are tCO2e, or total carbon dioxide equivalent per household).


Tilman Santarius give a nice talk about energy efficiency rebound effects, which is closely related to my previous post, where you can find more information. He discussed the interactions between energy efficiency, labor productivity, human behavior, and economic growth, and he distinguished between rebounds due to an income effect vs a substitution effect. In any case, average direct rebound effects appear to be around 20-30% (Greening et al. 2000; Sorell 2007), in addition to a 5-10% of indirect rebound. In other words, around 1/3 of income savings due to energy efficiency is lost because of an increase in energy demand. He also talked about the psychology of rebounds, including moral licensing (such as Prius drivers who drive more) and moral leakage (people feel less responsible). It will be a difficult task to try to separate energy demand from economic growth.

There were many other interesting talks, but I’ll end with the issue of climate adaptation and geoengineering. Ann Kinzig described how the combined risk of a phenomenon is the sum Σ p (event) × impact (event). Mitigation seeks to reduce the probability p while adaptation seeks to reduce the impact. Climate change will have impacts on food, water, ecosystems, and weather events, and decision-makers in urban areas can try to prepare for these (see this website). Kinzig also spoke about historical case studies of failed adaptations by people in the Hohokam (Arizona), Mesa Verde (Colorado), and Mimbres (New Mexico) regions, and the dependence on societal hierarchy and conformity. Alan Robock spoke about the risks and benefits of “geoengineering”, which involves gigantic projects in the future to address climate change, such as space-based reflectors, stratospheric aerosols, and cloud brightening (seeding clouds), and basically involve using the Earth as a science experiment with a huge cost of failure. In particular, he studies the many problems of injecting sulfate aerosols into the stratosphere to cool the planet. (Some people have supported this idea because of the supposedly benign effects of volcanic eruptions in the past.) He discussed the potential benefits of stratospheric geoengineering but compiled a list of 17 risks, including drought in Africa and Asia, continued ocean acidification, ozone depletion, no more blue skies, military use of technology, ruining terrestial optical astronomy, moral issues, and unexpected consequences. For more on Robock’s research and for other useful references, go here.